Halogen spots blowing fuse

[Dan12]

Hi everyone,

So this evening I was doing some work on our burglar alarm, reconnecting the dialer to the phone line after the previous telephone wire was mangled in some work we were getting done. The alarm is connected to a fused spur coming off one of the lighting circuits.

After reconnecting the alarm to the mains (i was pulling the fuse out a few times so i could connect the phone wires and check it worked) eveything was going fine. I'd had the lights on in the hallway. Later on when I came back all the lights were off and the burglar alarm had also gone off as its on the same circuit as those particular lights.

I thought maybe it was me connecting and disconnecting the alarm blew the fuse. I disconnected the alarm from the mains and put a new fuse in at the consumer unit, and it blew straight away. I managed to wittle the problem down to the halogen spots that I had on in the hallway.

Now if I keep the spots off the fuse stays fine and the lighting circuit works fine along with the burglar alarm. What I don't understand is that I wasn't actually doing any mains electrical work. If the bulb had blew in one of the spots surely it would just blow the fuse the once? But every time i put a new fuse in and turn on the spots they don't even flicker, they never come on and the fuse is gone.

Any ideas on this? I'm pretty baffled as i never touched the lights!

 

[flameport]

If the bulb had blew in one of the spots surely it would just blow the fuse the once?

Usually, but it is also possible for the lamp (bulb) to fail and create a short across the supply which will blow the fuse every time.

Remove all of the lamps and then see what happens.

 

[Dan12]

Thanks for your reply.

I had a closer look at the lights and realised theyre low voltage lights. I took both bulbs out and tried the switch again which blew the fuse. I'm thinking there must be a problem with the transformers?

Is it possible for transformers to just die like this? I'd say the lights have been in near enough 15 years.

 

[RF Lighting]

Yeah it sounds like it's just been an unlucky coincidence that this has happened at the same time as you were doing you bits with the alarm.

It is possible that a transformer has failed short circuit, but it's not that common. They usually fail open circuit and just stop working wothout taking the rest of the circuit out.

Drop each light out of the ceiling along with the transformers and the mains wiring too and check for any signs of over heating to anything.

It's not unknown of for a downlighter to toast the wiring to or the actual transformer it's self which can leave you with a short circuit.

If there is no sign of burning then it's just a case of tracking down which is the faulty tranny and swapping it out, and hopefully that will cure it.